Three Chinese performances of the South Korean soprano Sumi Jo were cancelled without explanation recently. The theory is that it is retaliation for South Korea's recent acceptance of a US missile defense system called THAAD in South Korea. A performance by Korean pianist Kun-woo Paik was also cancelled.

Sumi Jo is apparently a very well-known singer outside of the US (possibly among opera aficionados in the US as well). She has won a Grammy and was nominated for an Academy Award in 2016 for "Simple Song #3," which was featured in a 2015 Italian film named "Youth." She is amply represented on Youtube.

Although nominated for an Academy Award for "Simple Song #3" in 2016, Jo was not invited to perform the song at the award ceremany. Three other nominees were and did perform their songs. The only other nominee excluded in this way was a transgender singer named Ahnoni. Some considered this an example of the Academy's lack of diversity in a well-publicized campaign in 2016 known as #OscarsSoWhite. It must be noted, however, that #OscarsSoWhite focused primarily on the inclusion of African-American performers and, just anecdotally, I am not sure anyone in the US even remembers Sumi Jo's name in relation to this political campaign.

BEIJING — Sumi Jo, a Grammy Award-winning South Korean soprano, had been scheduled to perform alongside three top orchestras in mainland China.

One venue billed the performance as a “grand and worthy” tribute to the beloved opera singer Maria Callas by “one of the most sought-after Korean sopranos in the world.”

But on Sunday, about a month before the concerts were scheduled to take place, the three orchestras suddenly issued separate but seemingly coordinated notices announcing that Ms. Jo, a veteran coloratura soprano, would no longer be performing.

The cancellations have heightened suspicions that South Korean classical musicians are the latest casualties of political tensions with China that go back to July, when the government in Seoul announced that it would deploy a United States missile-defense system known as Thaad on its soil.

In statements published on their official WeChat social media accounts, three orchestras — the Shanghai Symphony, the Guangzhou Symphony, and the China Philharmonic in Beijing — offered little or no explanation for why Ms. Jo would not be performing.

The China Philharmonic noted that Ms. Jo and the South Korean conductor Min Chung had been “forced to withdraw” from the performance for “specific reasons.”

For the concerts in Guangzhou and Shanghai, Ms. Jo will be replaced by the Chinese soprano Ying Huang. In Beijing, her spot will be filled by the Chinese soprano Liping Zhang, while the Chinese conductor Yang Yang will replace Mr. Chung.

The Xi’an Concert Hall has also removed from its online performance calendar information about a concert that had been scheduled for March 25 and that was to feature Ms. Jo. It was not part of the Callas tribute series.

Ms. Jo’s performances with the Hong Kong Philharmonic on Feb. 3 and 4 appear to be unaffected. The semiautonomous region has a separate visa application process.

The announcements on Sunday came just days after a performance by the South Korean pianist Kun-woo Paik and the Guiyang Symphony Orchestra, scheduled for March in the Chinese province of Guizhou, was abruptly called off on Wednesday.

Based on Guiyang Symphony Orchestra’s website, it appears that Mr. Paik has been replaced in the program by the Chinese pianist Sa Chen.

“We never expected this to happen,” Ms. Jo’s brother, Jay Jo, said by telephone on Monday. “Sumi has toured nearly every year in China for almost 10 years.”

Many observers had been expecting various forms of Chinese retaliation after the announcement about the missile system. In August, several events in China featuring South Korean music and television stars were suddenly called off, setting off fears that the Chinese government was quietly going after K-pop, one of South Korea’s biggest cultural exports.

There has been no official confirmation of a Chinese blacklist or a ban on South Korean artists and entertainers. But “that’s the beauty of the Chinese government — they never say anything,” Mr. Jo said.

He added that the idea for the tribute concerts to Callas had been presented to Ms. Jo more than two years ago, and that the China tour dates had been confirmed in the summer.

When Ms. Jo was preparing to apply for an entry visa last month, Mr. Jo said, the Chinese orchestras were unable to provide the required government-approved invitation letter.

Reached by telephone on Monday, the Guangzhou Symphony Orchestra declined to comment. The China Philharmonic Orchestra and the Shanghai Symphony Orchestra did not respond to requests for comment sent by email and WeChat. The Chinese conductor Long Yu, who holds a leadership position in all three of the orchestras, did not respond to a call for comment.

Ms. Jo last performed in China in May, at a concert with the Spanish guitarist Pepe Romero at the National Center for Performing Arts in Beijing.

On Jan. 31, she will make her debut with the New York Philharmonic at its annual Chinese New Year concert. Mr. Yu will conduct.